The present invention concerns the field of chemical cleaning agents. In particular, tetrahydrofurfuryl alcohol mixtures with certain activators are disclosed which can replace the use of chlorofluorocarbons (CFCs) in the cleaning industry. As activators, compounds of the formula ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 are independently hydrogen, C.sub.1 -C.sub.7 ; alkyl, C.sub.5 -C.sub.6 cycloalkyl, furanyl which can be substituted by C.sub.1 -C.sub.7 ; alkyl, tetrahydrofuranyl which can be substituted by C.sub.1 -C.sub.7 alkyl, pyrrolyl, pyrrolidinyl, benzyl which can be substituted by C.sub.1 -C.sub.7 alkyl, phenyl which can be substituted by C.sub.1 -C.sub.7 alkyl, C.sub.1 -C.sub.7 alkenyl, C.sub.1 -C.sub.7 alkenyl, furfuryl which can be substituted by C.sub.1 -C.sub.7 alkyl, or tetrahydrofurfuryl which can be substituted by C.sub.1 -C.sub.7 alkyl, wherein R.sub.1, R.sub.2 and R.sub.3 can be substituted by at least one hydroxy group, provided that R.sub.1, R.sub.2 and R.sub.3 are not simultaneously hydrogen, or ##STR3## wherein R.sub.4 is hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 cycloalkyl, furanyl which can be substituted by C.sub.1 -C.sub.6 alkyl, tetrahydrofuranyl which can be substituted by C.sub.1 -C.sub.6 alkyl, pyrrolyl, pyrrolidinyl, or benzyl which can be substituted by C.sub.1 -C.sub.6 alkyl, is C.sub.1 -C.sub.6 alkyl, C.sub.5 -C.sub.6 cycloalkyl, furanyl which can be substituted by C.sub.1 -C.sub.6 alkyl, tetrahydrofuranyl which can be substituted by C.sub.1 -C.sub.6 alkyl, furfuryl which can be substituted by C.sub.1 -C.sub.6 alkyl, tetrahydrofurfuryl which can be substituted by C.sub.1 -C.sub.6 alkyl, pyrrolyl, pyrrolidinyl, benzyl which can be substituted by C.sub.1 -C.sub.6 alkyl, or the group EQU --(C).sub.a --O--(C).sub.b --O--(C).sub.b --OH
wherein a is from 1 to 3 and b is from 1 to 4, can be used.
In addition to the activators (I) or (II), the present invention can also include as activators cyclic or non-cyclic diamines, pyrrolidone which can be substituted by C.sub.1 -C.sub.6 alkyl or C.sub.1 -C.sub.6 alkenyl, or butyrolactone.
The use of THFA and the activators of this invention offer a response to adverse findings by the atmospheric science community that have recently led the federal Environmental Protection Agency to severely restrict the use of CFCs. In particular, it has been found that chlorine and bromine from CFCs and halons are a primary factor in the seasonal loss of ozone at the South Pole known as the Antarctic "ozone hole". In 1987 alone, 50% of the ozone layer over Antarctica was destroyed during September and October. On a global basis, the ozone layer has shrunk an average of about 2.5% during the past decade. Many experts in the atmospheric science community are of the opinion that although there has been no massive loss of ozone observed in the Arctic, this area shows a very high potential for significant change. (Cf. C&EN, Jul. 24, 1989.) Thus, it is particularly important that the chemical industry find alternatives to the CFCs in use today.
Approximately 23% of all CFCs in use today concern compounds that are used in the chemical cleaning industry.
Chlorofluorocarbons such as Freon.TM., 1,1,1-trichloroethane, trichloroethylene, methylene chloride and aqueous caustic cleaners have been frequently used in the industry. In general, the actual cleaning process involves boiling the chlorofluorocarbon in a sump to produce a vapor zone. A contaminated working piece to be cleaned is placed in the sump. After the working piece has been immersed in the boiling cleaning solution for several minutes, it is then lifted to the vapor zone. In the vapor zone, condensation occurs which causes the contaminants to be rinsed from the working piece. These contaminants are usually undesirable materials such as oil, grease or flux. Often, this process can be repeated two or three times for further cleaning. It is also known to arrange such a process on a continuous basis. For example, a conveyor belt system can be used.
After several cycles of cleaning, the cleaning solution becomes spent and must be reclaimed. Reclamation is usually accomplished by unloading the spent solution to a distillation unit where the CFC portion to be recycled is separated from the contaminating flux residue. The CFC portion is recovered as the overhead product from the distillation unit, is condensed in an overhead receiver, and recycled back to the solvent cleaning system.
At present, CFC solvent cleaning systems typically use a multiple sump arrangement coupled to a distillation unit. To maximize efficiency, it is known to use a vacuum distillation system. However, such a multiple arrangement of units must be carefully designed to limit the amount of CFCs escaping into the atmosphere. This is not only an extremely difficult design task, but a costly system to build. Due to these drawbacks, many shortcuts have been taken in building solvent cleaning systems. Thus, the final operating system all too often allows excess amounts of CFCs to escape into the atmosphere.
It is imperative that the currently used CFC compounds be replaced as quickly as possible to prevent any further erosion of the ozone layer of the atmosphere. In addition, it is highly desirable to replace these compounds with a material that offers a high efficiency of cleaning at standard temperature and pressure conditions to reduce dangers inherent to operations personnel.
As a replacement for CFC compounds used in the cleaning industry, the use of tetrahydrofurfuryl alcohol (THFA) has been suggested. It is known that THFA is an excellent solvent which is completely miscible with water. Moreover, a variety of formulations containing tetrahydrofurfuryl alcohol are used in industry for such applications as textile cleaners to remove gear grease from cloth, oven cleaners, solvents for epoxy coatings, production line cleaners for the removal of resin solder flux in the electronics industry, brush cleaners where melting agents are applied, and for wash cleaning semiconductor elements.
The present invention not only takes advantage of the cleaning properties of THFA but improves upon those properties. Thus, the present invention serves as a benefit to the environment by having the ability to replace CFCs in the chemical cleaning industry as well as offers a significant improvement to known environmentally acceptable cleaning agents.